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首页> 外文学位 >Theoretical Vibrational Spectroscopy of the E3B (Explicit Three-Body) Water Model and Evidence for a Liquid-Liquid Critical Point in Supercooled Water within This Model.
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Theoretical Vibrational Spectroscopy of the E3B (Explicit Three-Body) Water Model and Evidence for a Liquid-Liquid Critical Point in Supercooled Water within This Model.

机译：E3B（显式三体）水模型的理论振动光谱和该模型中过冷水中液体临界点的证据。

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摘要

Water, one of the most common substances on earth, is of tremendous importance for our daily life and many disciplines of science. Despite its simple molecular structure, water is very complicated and has many anomalies in condensed phases, mostly due to its vast and continuously changing hydrogen-bonding network. Experimentally, vibrational spectroscopy, especially in the OH bond stretch frequency region, is an ideal tool to investigate the microscopic structure and dynamics of this network. However, the interpretation of the experimental measurements usually needs the assistance of theoretical calculation. This thesis presents our recent work in simulating linear and non-linear vibrational spectroscopy of liquid water in diverse environments using a novel model. We believe our results provide new insights into this important and interesting field.;In this thesis, we use a newly developed water model, named E3B, which explicitly includes three-body interaction terms in its Hamiltonian. We begin with the simulation of the two-dimensional sum frequency generation spectroscopy at the water/vapor interface. The result reveals the slow hydrogen-bond switching dynamics at the water liquid/vapor interface. Then we evaluate the E3B model by comparing the temperature dependence of the theoretical non-linear vibrational spectra to experimental data. The result shows that the E3B model outperforms other commonly used models in terms of the microscopic dynamics of liquid water in a wide temperature range. Next, we propose a spectroscopic map for the water bend mode, and use it to study the vibrational spectra of this mode in the bulk liquid and the surface. The result has a reasonable agreement with the experimental data. We suggest that the bend mode, although studied less often than the OH-stretch mode, provides complementary information about the microscopic structure of water. At last, we discuss another interesting topic, which is the proposed liquid-liquid critical point of supercooled water. Using microseconds long simulation, we find evidence for the existence of a LLCP within the E3B model. We rationalize the result of our simulation by connecting this proposed critical point to the kink in the homogeneous nucleation line.
机译：水是地球上最常见的物质之一，对我们的日常生活和许多科学学科都至关重要。尽管其分子结构简单，但水非常复杂，并且在冷凝相中有许多异常，这主要是由于其庞大且不断变化的氢键网络。在实验上，振动光谱法，尤其是在OH键拉伸频率范围内，是研究该网络的微观结构和动力学的理想工具。但是，对实验测量的解释通常需要理论计算的帮助。本文介绍了我们最近在使用新型模型模拟各种环境中液态水的线性和非线性振动光谱方面的工作。我们相信我们的结果为这个重要而有趣的领域提供了新的见识。；在本文中，我们使用了一个新开发的水模型，名为E3B，该模型在其哈密顿量中明确包含了三体相互作用项。我们从水/蒸汽界面处的二维求和频率生成光谱的仿真开始。结果揭示了在水液/气界面处氢键转换动力学缓慢。然后，我们通过将理论非线性振动光谱的温度依赖性与实验数据进行比较，来评估E3B模型。结果表明，E3B模型在宽温度范围内的液态水微观动力学方面优于其他常用模型。接下来，我们提出水弯曲模式的光谱图，并使用它来研究该模式在大块液体和表面中的振动光谱。结果与实验数据吻合良好。我们建议，尽管弯曲模式的研究频率低于OH拉伸模式，但可以提供有关水的微观结构的补充信息。最后，我们讨论了另一个有趣的话题，即提出的过冷水的液-液临界点。使用微秒长的仿真，我们发现E3B模型中存在LLCP的证据。通过将建议的临界点连接到均匀成核线中的纽结，我们可以使仿真结果合理化。

著录项

  • 作者

    Ni, Yicun.;

  • 作者单位

    The University of Wisconsin - Madison.;

  • 授予单位 The University of Wisconsin - Madison.;
  • 学科 Physical chemistry.;Molecular physics.
  • 学位 Ph.D.
  • 年度 2016
  • 页码 133 p.
  • 总页数 133
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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